1. Field of the Invention
This invention relates in general to offshore drilling equipment, and in particular to a telescoping joint for connecting between a subsea housing and a housing carried by a jackup drilling rig.
2. Description of the Prior Art
In one system used with offshore jackup drilling rigs, a string of casing in the well will be supported by a mudline hanger located in a subsea housing at the sea floor. A section of the casing will extend upward to a surface wellhead housing at the drilling rig. The surface wellhead housing will be located above the sea and below the rig floor. The distance from the subsea housing to the surface wellhead could be as much as 500 feet with a large jackup drilling rig.
Cement will be pumped down the casing string to flow up the annulus to cement the casing in the well. The level of cement will be below the mudline hanger. In one prior art system, the casing will be cut off at the surface wellhead. The blowout preventer will be removed, and a spear will be used to pull tension on the casing after cementing. Then slips will be inserted around the casing which engage the wellhead housing and grip the casing to hold the casing in tension. A packoff will be installed between the casing hanger and the wellhead housing. A disadvantage of this prior art system is that the blowout preventer must be removed while installing the slips and packoff. Also, the prior art system is time consuming and expensive.
There are other proposals. In U.S. patent application Ser. No. 466,985, Steven A. Cromar, et al, filed January 18, 1990 now U.S. Pat. No. 5,002,131, a mechanism is employed for applying tension to the casing, utilizing spring biased locking elements which engage grooves in the wellhead housing. This allows the length of the casing from the subsea housing to the surface wellhead to be adjusted.
Telescoping joints have been used in the past with floating drill rigs. These telescoping joints utilize inner and outer conduits that will slide with one another due to wave action. Seals located between the inner and outer conduits will slidingly seal during the wave movement. A jackup drilling rig will not utilize a telescoping joint of this type because it will not be floating during drilling operations.